Process for preparing polyurethane polyol and rigid foams therefrom from cardanol

ABSTRACT

The present invention provides a process for the preparation of polyurethane polyol from cardanol, derived from cashew nut shell liquid, a renewable resource material. The polyol is made by oxidation with peroxy acid generated in-situ to give epoxidised cardanol and the said epoxy derivative is converted to the polyol in the presence of the organic acid. According to another aspect of the present invention the cardanol-based polyol formed by the novel method of this invention may be reacted with isocyanate to form polyurethane. Alternatively blowing agents are included with the cardanol-based polyol before it is reacted with the isocyanate. These polyols are especially suitable for making rigid foams of very low density and high compressive strength.

FIELD OF THE INVENTION

The present invention relates to a process for the preparation ofpolyurethane polyol from cardanol and rigid foams therefrom. The processprovides polyurethane polyols suitable in the preparation of rigidpolyurethane foams starting from a renewable resource material, CashewNut Shell Liquid (hereinafter abbreviated as CNSL).

BACKGROUND OF THE INVENTION

The disclosed novel polyol is derived from cardanol, a product obtainedfrom natural CNSL and is the main constituent of technical grade CNSL.Cashew Nut Shell liquid has been known for years to contain compoundsuseful in varoious aspects of chemical industry. Technical grade ordistilled CNSL is a commercially available product. It comprises inmajor proportions (typically more than 95% by weight) a material alsosold separately under the trade name cardanol, which is a substitutedphenol possessing an alkyl chain of average unsaturation two doublebonds in the meta position. Other minor constituents are cardol and2-methyl cardol. Cardanol is used in many industrial applications suchas coatings, resins, adhesives and other novel products. Novel polyolsof the present invention are used in making rigid PU foams. The reactionof diisocyanate and or poly isocyanate with the hydroxyl groups ofpolyol co reactants and blowing agents (such as water, dichloromethane,cyclopentane and HCFC's) are used to produce polyurethane foams. Rigidpolyurethane foams are primarily used for thermal insulation.Polyurethane foams constitute the largest category of cellular polymericmaterials. They offer an attractive balance of performancecharacteristics such as aging properties, mechanical strength, elasticproperties, and chemical resistance, insulating properties and cost.

Polyols based on petroleum resources are costly and scarce. Some of themsuch as polyester polyols also possess poor resistance to hydrolysis andpoor abrasion resistance. It is of particular interest to developpolyols which may be easily and cheaply obtained form readily availableand renewable resource material such as CNSL. Its use in the preparationof polyurethane polyols suitable for making rigid foams is not reported.For the preparation of polyols from renewable resources like vegetableoils several processes are disclosed in the literature. Reference may bemade to U.S. Pat. No. 6,107,433 which disclose process for preparingvegetable oil based polyol from castor oil by oxidation of the sidechain unsaturation using per acids and a method for making polyurethanecastings using these polyols. In another patent [U.S. Pat. No.4,825,004] a process for the production of alkane polyols starting fromnatural fatty acid derivatives by per acid oxidation is disclosed.However, these prior art processes have not been reported with cardanolbefore for making polyurethane polyols. Because of the unique molecularstructure of cardanol (a long unsaturated side alkyl chain on thebenzene ring) the disadvantages disclosed in the prior art process, isnot applicable in the case of cardanol. For example, the hydrolysis oftriglyceride oils is not expected in the case of cardanol.

OBJECTS OF THE INVENTION

The object of the present invention is to provide a Process for thePreparation of Polyurethane Polyol from Cardanol and Rigid Foamstherefrom.

Still another object of the present invention is to provide a method formaking cardanol based Polyols having a desirable viscosity and highcontent of hydroxyl groups.

Yet another object of the present invention is to provide a rigid PUfoam, made form Cashew Nut Shell Liquid based polyols having improvedmechanical, hydrolytic stability and insulation properties overconventional rigid foams and a method for making such polyols so is thatrigid foam having excellent insulating properties may be provided.

Still another object of the present invention is to provide a method formaking various cardanol based polyols having a favorable distribution ofhydroxyl groups in the molecule so that these polyols are reacted withisocyanantes.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

In the drawing accompanying this specification FIG. 1 represents thegeneral scheme for the peracid oxidation and subsequent hydrolysisstarting with the diene component (I) of cardanol.

SUMMARY OF THE INVENTION

Accordingly the present invention provides a process for the preparationof polyurethane polyol from cardanol and rigid foams therefromcomprising oxidising technical grade Cashew nut shell liquid containingcardanol as the main component (>95%) with a peracid generated in situfrom hydrogen peroxide and an organic acid in presence of a catalyst, inorder to oxidise the unsaturation in the side chain of cardanol, theratio of cardanol to H₂O₂ employed being 1:2, the ratio of cardanol toorganic acid is 1:1, the ratio of cardanol to organic acid to hydrogenperoxide being 1: 1:2, the reaction temperature being in the range of 0°and 80° C., maintaining the mixture at the reaction temperature toproduce a hydroxy-formoxy ester, subjecting the hydroxy-formoxy ester tohydrolysis with sodium acetate to produce the polyol, and separating thepolyol from the unreacted reactants, and reacting the polyol withisocyanate and blowing agent under suitable conditions to obtain a rigidfoam.

In one embodiment of the invention, the organic acid is selected fromthe group consisting of formic acid and acetic acid.

In one embodiment of the invention, the catalyst is 10% H₂SO₄.

In one embodiment of the invention, the starting material is extractedfrom seeds of Anacardium oxidentale by high temperature distillationunder vacuum.

In one embodiment of the invention, the polyol obtained has a hydroxylvalue in the range of 200-600 typically 350-400 mg KOH/g and viscosityless than 250 poise, typically 100 poise.

In one embodiment of the invention, the reaction temperature ispreferably in the range of 25-35° C.

In one embodiment of the invention, wherein an intermediate productcomprising an epoxide is produced which is hydrolyzed to an esteralcohol in the presence of excess acid.

In one embodiment of the invention, wherein an intermediate productcomprising a hydroxyester is obtained which is hydrolyzed to the polyolusing alkali.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

FIG. 1 is a non-limiting representation of the reaction scheme of theprocess of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a process for the preparation ofpolyurethane polyol from cardanol and rigid foams therefrom whichcomprises treatment of cardanol or technical CNSL whereby theunsaturation present in the side chain gets oxidized using the peracidgenerated insitu from a peroxide and organic acid, such as formic oracetic acid in presence of a mineral acid catalyst like H₂SO₄ and thepreferred ratio of cardanol to formic acid is 1:1 or ratio of cardanolto H₂O₂ 1:2 and the process is carried out at temperatures between 0-80°C., preferably 25-35° C. to give the ester alcohol which is hydrolyzedunder alkaline conditions to produce the product polyol that isseparated from the uncombined reactants to produce the product polyol.

The process of adding a peroxide to cardanol and formic or acetic acidwhere in the peroxy acid generated in-situ reacts with cardanolunsaturation to form epoxidised cardanol and the epoxidised cardanol inpresence of excess acid is converted to the hydroxyl ester, hydrolyzedby alkali to give the polyol. In another embodiment a process for thepreparation of polyols from cardanol especially suitable in the makingof rigid polyurethane foams by oxidation with per acids, the uniquemolecular structure of cardanol allows the use of a variety of peracids, which can be prepared, in situ in the hydroxylation reaction andthe product polyol is useful for making rigid foam, composites, and PUplastics and it has low viscosity and high hydroxyl functionalityobtained using the formulation comprising of technical CNSL, 30% H₂O₂,HCOOH, CH₃COOH and a catalytic amount of H₂SO₄ and an alkali. Anoxidation reaction suitable for the conversion of olefins to epoxide andsubsequently to hydroxyl function is described. A method for making thePU foam from the developed polyols is also disclosed. The methodincludes mixing together of the dried polyol, blowing agent, isocyanate,and catalyst in suitable cup of standard dimensions.

The present invention disclosing the synthesis of polyol based onrenewable resource material has been developed for various applications.The disclosed novel polyol is derived from cardanol, a product obtainedby treating cashew nut shell liquid. CNSL consists primarily ofanacardic acid which is decarboxylated when heated in the presence ofacid giving cardanol; a meta substituted phenol used in this invention.The side chain in cardanol contains an average of two double bond permolecule, which on oxidation with peracid and subsequent saponificationyields tetra functional polyols. One particular use is for making rigidpolyurethane foams. Polyols useful in the preparation of rigid foamsshould have specific foam rise characteristics as tested by the cup foammethod, the preferred method for evaluating the polyols in making rigidfoams.

The method of the present invention involves making cardanol-basedpolyols by converting the double bond s present in the alkenyl chain into hydroxyl groups. This method takes place at approximately atmosphericpressure.

The process of the present invention involves epoxidation and subsequenthydroxylation of cardanol so as to make a polyol. More specifically theprocess of the present invention involves adding a peroxide in thepresence of an organic acid to generate the per acid in situ wherein theperacid and cardanol react to form epoxidised cardanol, the saidepoxidised product undergoes conversion to ester and hydroxyl compound.These are consecutive non-stop processes as the intermediate product isdirectly subjected to the next step without further isolation andpurification. The reaction is not stopped after the epoxidised cardanolso as to purify the intermediate product.

Any peroxy acid may be used in the reaction. Example of peroxy acidsthat may be used include, but are not limited to, peroxy formic acid,peroxy acetic acid, trifluoroperoxyacetic acid, benzyloxyperoxy formicacid, m-chloroperoxybenzoic acid, or any combination of these peroxyacids. The peroxy acids may be formed in situ by reaction of ahydroperoxide with the corresponding acid, such as formic acid or aceticacid. Examples of hydro peroxides that may be used include, but are notlimited to, hydrogen peroxide, t-butyl hydro peroxides, triphenyl silylhydro peroxides, cumyl hydro peroxides, or any combination of thesehydro peroxides. Preferably the peroxy acid is in a solvent such asformic acid, acetic acid, chloroform, or ethyl acetate.

Water is also an important constituent of this reaction; it reacts withthe epoxy groups of the epoxidised cardanol to form two hydroxyl groupsper epoxy group in some location so as to increase the hydroxyl contentof the cardanol based polyols. Specifically water contributes to a fewpercent (5-10%) of the hydroxylation.

The catalyst, which is useful in the invention, includes mineral acidslike 10% H₂SO₄.

Water washing is used to remove the excess acid or alkali present in theproduct.

The epoxidation reaction occurs approximately at room temperature andtemperature should be controlled between 0-80° C. and the preferredtemperature is 35° C. for the per formic acid oxidation.

Higher reaction temp can cause the reaction to become violent. Thereaction is finished in 30 to 36 hours after that all the reactants aremixed together.

The cardanol based polyol made by the method of the present inventionhave viscosity in the range of 5000-9000 centipoise at room temperature.Still further the polyols made by the, method of the present inventionhave hydroxyl values ranging from 350-400 mg/KOH per g determined inaccordance with method ASTM D 1957 (1963). The cardanol based polyolscan be made in yields of 80-95% using any of the various embodiments ofthe present invention.

This method of making the polyols is illustrated in the followingexamples. These examples are not meant in any way to limit the scope ofthis invention.

EXAMPLE 1

A mixture of 7.82 g of formic acid [0.17 mole] and 50 g of cardanol[0.17 mole] is taken together in a glass vessel and the mixture understirring is cooled to 0° C. While stirring continued and maintaining thetemperature, 38.5 g (0.34 mole) of 30% H₂O₂ is added drop wise from apressure equalizing funnel. The addition time required 5-10 hours.During addition the temperature is maintained by a cooling bath.

After completion of the addition, the reaction temperature is increasedto 35° C., whereby the epoxy groups present is converted tohydroxyl-formoxy ester. The half ester so produced is hydrolyzed withsodium acetate at 80° C. for 4 hours. The product is neutralized, washedwith excess water till neutral to litmus and dried over anhydrous sodiumsulphate.

EXAMPLE 2

A mixture of 20 g of formic acid [0.57 mole] and 151 g of cardanol [0.5mole] is taken together in a glass vessel and the mixture under stirringis cooled to 0° C. while stirring continued and maintaining temperature116 g 30% (1.02 mole) H₂O₂ is added drop wise from a pressure equalizingfunnel. The addition is completed in 5-10 hours. During addition thetemperature is maintained by a cooling bath.

After the complete addition, the reaction temperature is increased to35° C., whereby the epoxy groups present is hydrolyzed tohydroxyl-formoxy ester. The half ester so produced is hydrolyzed withsodium acetate at 80° C. for 4 hours. The product is neutralized, washedwith excess water till neutral to litmus and dried over anhydrous sodiumsulphate.

EXAMPLE 3

In another example a mixture of 19 g of formic acid [0.6 mole] and 150 gof cardanol [0.5 mole] is taken together in a glass vessel and themixture stirred at cooled to 0° C. while stirring continued andmaintaining temperature 115 g 30% (1.02 mole) H₂O₂ is added drop wisefrom a pressure equalizing funnel. The addition is required 5-10 hours.During addition the temperature is maintained by ice cooling at 24-32°C.

After complete addition, the reaction temperature is increased to 35°C., whereby the epoxy groups present is hydrolyzed to hydroxyl-formoxyester. The half ester so produced is hydrolyzed with sodium acetate at80° C. for 4 hours. The product is neutralized, washed with excess watertill neutral to litmus and dried over anhydrous sodium sulphate.

The mineral acid catalyst such as conc H₂SO₄ is used in an amount 0.05%to 5% on the weight of cardanol. At the end of the reaction the productis taken in a separating funnel washed with excess of water till neutralto litmus and dried over anhydrous sodium sulfate. The dried polyol hasthe following characteristics. Yield 80-98 % Viscosity—100-220 Poisetypically less than 250 Poise. Hydroxyl value—200-600 preferably 350-400mg KOH/g Acid value less than 5.

In forming the polyurethane, the isocyanate reacts with the hydroxylgroups of the cardanol polyol. The polyol and the isocyanate are mixedin approximately stoichiometric quantities. It is agreeable to use up toabout 10% in excess of the stoichiometric quantity of either of thesecomponents. Examples of isocyanate that can be selected include, but arenot limited to polymeric or crude biphenyl methane diisocyanate (MDI),modified MDI including hydrogenated MDI Isophrone Diisocyanate (IPDI) or2,4-toluene diisocyanate(TDI). The preferred isocyanate is a polymericMDI, for example (Suprasec X-2185) having an isocyanate content of22-31% available form the ICI polyurethane's, Belgium, Lupranate. M20Sor Lupranate M70R from BASF or MONDUR MA2601 from BAYER corporation.

Reaction of the polyol with isocyanate such as MDI forms thepolyurethane by known methods in the art. The isocyanate is included inthe composition to provide a 1:1 mole ratio or more preferably % byweight.

Blowing agents are included in the formulation, typically in proportionsof 4-6% by weight.

A catalyst for the isocyanate water reaction is included in theformulation.

A second catalyst for the isocyanate polyol reaction is included in theformulation.

The rigid foam can be formed by mixing together the polyol with theblowing agent, conditioned at 22° C. under atmospheric pressure. Thecomponents are preferably mixed to a homogeneous mass, after the mixingthe composition is allowed to rise. The foams prepared can beadvantageously used in refrigeration where low thermal conductivity isrequired.

Polyurethane foams based on such cradanol based polyols is expected tohave higher thermal stability both in air and nitrogen and lower waterabsorption than corresponding polyurethane compounds based onpolypropylene oxide (PPO) polyols, and compared to other vegetable oilbased polyurethane's have better hydrolytic stability and lowerabsorption of water than corresponding PPO based foams. Still furtherthis foam has density comparable to the PPO based foams.

The following example illustrates the preparation of PU that may beprepared using cardanol based polyol. These examples are not meant inany way to limit the scope of this invention;

EXAMPLE 4

12.46 g of polyol, the product of example 2, 17.59 parts Suprasec X 2185(MDI), and 5.47 part of blowing agent and 2.8 part of catalyst weremixed.

The polyol mixed with the blowing agent and isocyanate was conditionedat 20° C. for 4 hours. The polyol and isocyanate component were weighedto the cup and stirred for 2 sec. Using a stirrer of standard design formaking the cup foam. And allowed to rise freely.

A cup foam test shows the following characteristics. They have typicallycream time 10-16 sec, string time 65-95 sec, end of rise time 110-165sec and tack free time of 160 sec., till the foaming stopped. The foamsproduced have a compressive strength of 0.038 N/mm² and density (26.59gm/cm³) quite comparable to the PPO polyol based foams.

The foams produced have regular cell structure as evidenced by ScanningElectron Microscopy.

From the foregoing, it will be seen that this invention is one, welladapted to obtain all the ends and objects herein above set forthtogether with other advantages which are obvious and inherent to thestructure. It will be understood that certain features and subcombinations are of utility and may be employed without reference toother features and sub combinations. Since many possible embodiments maybe made of the invention without departing from the scope thereof, it isto be understood that all matter herein set forth is to be interpretedas illustrative and not in a limiting sense.

REFERENCES

[US Patent Documents] month/year Authors U.S. Pat. No. 6107433August/2000 Petrovic et al. U.S. Pat. No. 4825004 April/1989 Ratzen etal

OTHER REFERENCES

-   Gedam et al Examination of the Components of Cashew Nut shell Liquid    by NMR Indian Journal of Chemistry vol. 10, 388-391,1972.-   C.K.S.Pillai, Polymeric materials from renewable Resources: High    value polymers from cashew nut shell liquid, Popular Plastics and    Packaging (special Issue) 79-84, 86-90, 2000.

1. A process for the preparation of polyurethane polyol from cardanoland rigid foams therefrom comprising oxidising technical grade Cashewnut shell liquid containing cardanol as the main component (>95%) with aperacid generated in situ from hydro peroxide and an organic acid inpresence of a catalyst, in order to oxidise the unsaturation in the sidechain of cardanol, the ratio of cardanol to hydroperoxide employed being1:2, the ratio of cardanol to organic acid is 1:1, the ratio of cardanolto organic acid to hydro peroxide being 1:1:2, the reaction temperaturebeing in the range of 0° and 80° C., maintaining the mixture at thereaction temperature to produce a hydroxy-formoxy ester, subjecting thehydroxy-formoxy ester to hydrolysis with sodium acetate to produce thepolyol, and separating the polyol from the unreacted reactants, and ifdesired, reacting the polyol with isocyanate and blowing agent to obtaina rigid foam.
 2. A process as claimed in claim 1 wherein the organicacid is selected from the group consisting of formic acid and aceticacid.
 3. A process as claimed in claim 1 wherein the catalyst is 10%H₂SO₄.
 4. A process as claimed in claim 1 wherein starting material isextracted from seeds of Anacardium oxidentale by high temperaturedistillation under vacuum.
 5. A process as claimed in claim 1 whereinthe polyol obtained has a hydroxyl value in the range of 200-600typically 350-400 mg KOH/g and viscosity less than 250 poise, typically100 poise.
 6. A process as claimed in claim 1 wherein the reactiontemperature is in range of 25-35° C.
 7. A process as claimed in claim 1wherein an intermediate product comprising an epoxide is produced whichis hydrolyzed to an ester alcohol in the presence of excess acid.
 8. Aprocess as claimed in claim 1 wherein an intermediate product comprisinga hydroxyester is obtained which is hydrolyzed to the polyol usingalkali.
 9. A process as claimed in claim 1 wherein the peroxy acid isselected from the group consisting of peroxyformic acid, peroxyaceticacid, trifluoroperoxyacetic acid, benzyloxyperoxy formic acid,m-chloroperoxybenzoic acid and any combination thereof
 10. A process asclaimed in claim 1 wherein the hydro peroxide is selected from the groupconsisting of hydrogen peroxide, t-butyl hydro peroxides, triphenylsilyl hydro peroxides, cumyl hydro peroxides and any combinationthereof.
 11. A process as claimed in claim 9 wherein the peroxy acid isin a solvent selected from the group consisting of formic acid, aceticacid, chloroform, and ethyl acetate.